fix: install miniflare extension from local checkout instead of git URL

The git URL approach with a slashed branch name (fix/ci-failures) causes
pip inside the LocalStack extensions venv to fail. Since the code is
already checked out by actions/checkout, install directly from the local
path to avoid any git URL branch-name parsing issues.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: whummer

.github/workflows/miniflare.yml

@@ -34,10 +34,8 @@ jobs:
           sudo apt-get install -y libvirt-dev
           pip install localstack localstack-ext
 
-          branchName=${GITHUB_HEAD_REF:-main}
-          echo "Installing from branch name $branchName"
           localstack extensions init
-          localstack extensions install "git+https://github.com/localstack/localstack-extensions.git@${branchName}#egg=localstack-extension-miniflare&subdirectory=miniflare"
+          localstack extensions install "file://$(pwd)/miniflare"
 
           DEBUG=1 localstack start -d
           localstack wait